This invention relates to a method and apparatus for detecting the presence of micro-organisms.
The need presently exists, in a great variety of applications, for detecting the presence of micro-organisms, especially bacteria of various types. In clinical medicine and medical research, it is frequently necessary to determine the bacteria count of blood, urine or tissue cultures. In the food and drug industry, it is essential that lots be tested for purity to insure safe consumption of the product.
Various methods have been proposed for such testing. For example, in laboratory testing it has been suggested that the sample be mixed with a radioactive nutrient medium in a flask and a cup containing a CO.sub.2 absorbing material be held above the medium to collect gas emitted by any bacteria (Warburg apparatus). The cup is then removed from the flask and the absorbing material mixed with a liquid scintillation solution. The light emitted from the solution as a result of the CO.sub.2 contained in the material is then measured by a scintillation counter. It will be realized that this process is fairly cumbersome and would not be entirely suitable for testing on a large scale. In addition, exposing the sample and the CO.sub.2 absorbing material to the ambient could lead to contamination. Furthermore, only a small amount of CO.sub.2 can be absorbed by that method and sensitivity is reduced. Other methods have been proposed utilizing the concept of measuring the CO.sub.2 emitted by micro-organisms during a life-support process, whether for measuring directly the sterility of a sample or for the distinctly different objective of determining the efficacy of a sterilization process by including a special chamber in the sterilizing atmosphere (see for example, U.S. Pat. No. 3,657,073 and U.S. Pat. No. 3,313,712). Presently available methods usually suffer from one or more of the problems of unreliability, contamination, ineffectiveness of separating nutrient medium from detection means, or excessively costly or complex equipment. It is therefore a primary object of the present invention to provide a reliable apparatus and method for detecting micro-organisms with a minimum number of processing steps and utilizing inexpensive, disposable apparatus to permit testing on a large scale.